The basking shark is the largest fish in the waters around Ireland and the second largest fish in the sea (the largest being the whale shark). It is east to identify, because of its size (usually around 7m to 11m). It has five very large gill slits with a pointed snout and a huge mouth it usually swims close to the surface with its first dorsal fin, snout and tail fin visible. The shark is grayish-brown to black with lighter mottling and the gills are bright red.
Basking sharks are active all year round; they do not hibernate as was once thought. In spring and summer they are usually seen at the surface swimming with their mouths wide open, mainly on days when the sea is calm enough to distinguish its fins breaking the surface. The Old Head of Kinsale, Oysterhaven and outside Cork harbour are good places to spot basking sharks in late spring. Despite its enormous size it feeds on planktonic organisms such as tiny crustaceans, jelly-fish and comb-jellies. In winter they move off shore into deep water where they feed on deepwater plankton.
Little is known about Basking shark reproduction but it is known that females give birth to live young. It is believed that female do not reach sexual maturity until they are 8m long while males are 5M. This means that these sharks are around 18 years before they reproduce. They are now protected in Irish water.